Gamstorp1 in 1956 described 17 cases of periodic weakness in 2 families, with normal or slightly elevated serum potassium levels during attacks. Contrary to attacks of weakness occurring in familial periodic paralysis, orally administered potassium chloride, instead of relieving, precipitated these attacks or made them worse. Gamstorp termed this anomaly adynamia episodica hereditaria. She emphasized that the typical inability to relax after muscle contraction in myotonia congenita is not seen during or between attacks of adynamia episodica hereditaria.
In 1941, Talbott2 collected 400 cases of periodic paralysis from the literature. The familial type of the disease appeared to be three times as common among males as among females. The musculature innervated by the cranial nerves and the respiratory musculature were seldom involved. The serum potassium level during the attacks, when determined, was found to be decreased.
Van Der Meulen3 and co-workers describe a patient admitted to the
FAMILIAL HYPERKALEMIC PARALYSIS WITH MYOTONIA. JAMA. 1961;176(9):805-806. doi:10.1001/jama.1961.03040220053013